The broad, long-term objective of the project is to determine whether neurodegenerative disease occurs as a result of deleterious mutations in the mitochondrial DNA (mtDNA) of neurons in affected regions of the brain. The current research focuses on Alzheimer's disease (AD). There are two specific aims. First, I will use a variety of histochemical techniques to identify pathologically impaired or vulnerable neurons in AD and age-matched control brain regions. Techniques for establishing the routine neuropathological diagnosis of AD and for the evaluation of mitochondrial pathology will be applied. I will use combination approaches to establish any link between classical AD pathology and mitochondrial pathology. Second, l will use laser-capture micro dissection (LCM) to extract single neurons stained in Aim 1 from both AD and unaffected controls. Using a PCR-based approach optimized for the amplification of full-length mtDNA from single cells (mt-XL-PCR), I will examine the mtDNA present in stained and control neurons. When large-scale deletions are present in mtDNA, the mt-XL-PCR technique results in amplification of a full-length product and one or more smaller products, derived from the mtDNA with deletions (dmtDNA). By examining the results of mt-XL-PCR in stained and unstained neuronal subsets, I will examine any link that may exist between the presence of mitochondrial genetic lesions and both classical and mitochondrial functional pathology in the AD brain, as compared to controls. Sequencing studies will allow for a precise characterization of any such dmtDNA lesions.